Monomeric carotenoids, excited states

While excited-state properties of monomeric carotenoids in organic solvents have been the subject of numerous experimental and theoretical studies (Polfvka and Sundstrom 2004), considerably less is known about excited states of carotenoid aggregates. Most of the knowledge gathered so far stems from studies of aggregation-induced spectral shifts of absorption bands of carotenoid aggregates that are explained in terms of excitonic interaction between the molecules in the aggregate. 

Kinetics recorded at the maxima of the Sj-S bands, monitoring dynamics of the lowest excited state, have revealed further differences, Figure 8.8. Although monoexponential decays have been observed for monomeric carotenoids (9ps for zeaxanthin and 24 ps for ACOA), aggregates exhibit more complicated decay patterns. The Sx decay of the H-aggregate requires at least four decay... 

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